1. Field of the Invention
This invention relates to the use of selected sulfonated polyethers as agents for preventing the static charging of plastic surfaces.
2. Description of Relevant Art
Due to their high volume resistivity, plastics have the property of accumulating electrical charges at their surfaces. This static charging of plastics, which is particularly serious in the presence of friction, is generally undesirable and attempts have long been made to prevent charging, either permanently or temporarily by a variety of measures, but especially by the inclusion of special additives, so-called antistatic agents. Thus, substances added to the plastics before molding are known as internal antistatic agents while substances applied subsequently to the surfaces are known as external antistatic agents.
The wide variety of compounds which have already been proposed for this purpose is in itself proof of the fact that a universal antistatic agent, i.e. one which is equally suitable for all plastics and applications, has not yet been found. On the contrary, most of the proposed compounds show weaknesses in many plastics, including inadequate compatibility, reluctance to accumulate at the surface or minimal adhesion to the surface, or, alternatively, only act under certain conditions such as, for example, high relative air humidity. Others can be used to only a limited extent due to their toxic properties or their color.
Particular importance is now attached to antistatic agents in the textiles field, firstly because the percentage of synthetic fibers is continuously increasing and secondly because manufacturers are using increasingly faster machines in which the fibers are exposed to extremely severe friction. In this specialized field also there are no universal antistatic agents either for the processing of endless fibers (filaments) and staple fibers or for the treatment of semi-finished and finished products. One particular problem in this respect is the antistatic finishing of polyamide fibers despite the fact that polyamide (PA) has a higher affinity for water than other synthetic fiber materials, such as polyester (PES) or polyacrylonitrile (PAC). The external antistatic agents commonly used today, such as for example ethoxylated fatty amines, long-chain phosphoric acid partial ester salts and long-chain paraffin sulfonate salts, always produce at most a temporary reduction in the electrostatic charging of PA, losing their effectiveness after periods of a few days or a few weeks. The reasons for this loss of activity have not yet been explained.